[PATCH v8 15/15] x86: EFI stub DRTM launch support for Secure Launch

Ross Philipson
2024-02-14T22:32:19Z

This support allows the DRTM launch to be initiated after an EFI stub
launch of the Linux kernel is done. This is accomplished by providing
a handler to jump to when a Secure Launch is in progress. This has to be
called after the EFI stub does Exit Boot Services.

Signed-off-by: Ross Philipson <ross.philipson@oracle.com>
---
drivers/firmware/efi/libstub/x86-stub.c | 55 +++++++++++++++++++++++++
1 file changed, 55 insertions(+)

diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
index 0d510c9a06a4..4df2cf539194 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -9,6 +9,7 @@
#include <linux/efi.h>
#include <linux/pci.h>
#include <linux/stddef.h>
+#include <linux/slr_table.h>

#include <asm/efi.h>
#include <asm/e820/types.h>
@@ -810,6 +811,57 @@ static efi_status_t efi_decompress_kernel(unsigned long *kernel_entry)
return EFI_SUCCESS;
}

+static void efi_secure_launch(struct boot_params *boot_params)
+{
+ struct slr_entry_uefi_config *uefi_config;
+ struct slr_uefi_cfg_entry *uefi_entry;
+ struct slr_entry_dl_info *dlinfo;
+ efi_guid_t guid = SLR_TABLE_GUID;
+ struct slr_table *slrt;
+ u64 memmap_hi;
+ void *table;
+ u8 buf[64] = {0};
+
+ table = get_efi_config_table(guid);
+
+ /*
+ * The presence of this table indicated a Secure Launch
+ * is being requested.
+ */
+ if (!table)
+ return;
+
+ slrt = (struct slr_table *)table;
+
+ if (slrt->magic != SLR_TABLE_MAGIC)
+ return;
+
+ /* Add config information to measure the UEFI memory map */
+ uefi_config = (struct slr_entry_uefi_config *)buf;
+ uefi_config->hdr.tag = SLR_ENTRY_UEFI_CONFIG;
+ uefi_config->hdr.size = sizeof(*uefi_config) + sizeof(*uefi_entry);
+ uefi_config->revision = SLR_UEFI_CONFIG_REVISION;
+ uefi_config->nr_entries = 1;
+ uefi_entry = (struct slr_uefi_cfg_entry *)(buf + sizeof(*uefi_config));
+ uefi_entry->pcr = 18;
+ uefi_entry->cfg = boot_params->efi_info.efi_memmap;
+ memmap_hi = boot_params->efi_info.efi_memmap_hi;
+ uefi_entry->cfg |= memmap_hi << 32;
+ uefi_entry->size = boot_params->efi_info.efi_memmap_size;
+ memcpy(&uefi_entry->evt_info[0], "Measured UEFI memory map",
+ strlen("Measured UEFI memory map"));
+
+ if (slr_add_entry(slrt, (struct slr_entry_hdr *)uefi_config))
+ return;
+
+ /* Jump through DL stub to initiate Secure Launch */
+ dlinfo = (struct slr_entry_dl_info *)
+ slr_next_entry_by_tag(slrt, NULL, SLR_ENTRY_DL_INFO);
+
+ asm volatile ("jmp *%%rax"
+ : : "a" (dlinfo->dl_handler), "D" (&dlinfo->bl_context));
+}
+
static void __noreturn enter_kernel(unsigned long kernel_addr,
struct boot_params *boot_params)
{
@@ -934,6 +986,9 @@ void __noreturn efi_stub_entry(efi_handle_t handle,
goto fail;
}

+ /* If a Secure Launch is in progress, this never returns */
+ efi_secure_launch(boot_params);
+
/*
* Call the SEV init code while still running with the firmware's
* GDT/IDT, so #VC exceptions will be handled by EFI.
--
2.39.3